Animal and human cell lines, particulariy those derived from patients, are crucial for isolating large quantities of genomic DNA and RNA, and for preparing protein extracts for Western blotting studies as well as enzyme analysis. Genomic DNA can be prepared from lymphocytes isolated from whole blood. However, the availability of immortalized B-lymphoblasts or primary skin fibroblasts from the patient is particularly advantageous for several reasons. Cell lines provide a reliable means of securing additional DNA when necessary without disturbing the patient and family members in additional venipunctures. It is also a safeguard, especially in the case of morbid (fatal) disease, to ensure DNA, RNA and protein sources for pathogenesis studies and for repeated analysis when new information and technology become available. In addition, cell lines are used for electroporation and viral infections in studies involving transient and long term expression. Lastly, fibroblasts from patients with IDD are likely to prove valuable in the future for induction into pluripotent mechanistic studies and potentially for screening for therapeutics.